HPC Discussion
Posted by JAC on 12/25/2010, 4:02 pm
MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
138 PM EST SAT DEC 25 2010

VALID DEC 25/1200 UTC THRU DEC 29/0000 UTC


...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR
INGEST...  

FINAL 12Z MODEL EVALUATION INCLUDING THE 12Z ECMWF

MODEL INITIALIZATION ERRORS ARE DESCRIBED UNDER THE RELEVANT
SYSTEM HEADING.

UPCOMING EAST COAST STORM...

THE MORNING SHORT RANGE MODELS CONVERGE.

THE 12Z NAM IS CONSISTENT WITH THE PAST 3 RUNS THROUGH AROUND
SUNDAY AFTERNOON WHEN THERE IS SLIGHT JOG FARTHER NORTHWARD AS THE
LOW IS MOVING TOWARD SOUTHERN NEW ENGLAND.  SUCH A JOG HAS SOME
IMPLICATIONS...THOUGH SLIGHT...IN THAT THE CYCLONE CENTER WOULD BE
20 TO 30 MILES FARTHER NORTH NORTHWEST THAN PREVIOUS RUNS.

THE 12Z GFS HAS A SUBTLE BUT SIGNIFICANT CHANGE FROM THE PREVIOUS
2 RUNS WITH THE SURFACE LOW BEING FARTHER NORTHEAST THAN PREVIOUS
RUNS.  BY SUNDAY/18Z WITH A RAPIDLY DEEPENING LOW EAST OF THE
VIRGINIA/MARYLAND COAST...THE 12Z GFS IS ABOUT 40 MILES NORTHEAST
THAN THE PREVIOUS RUN. BY MONDAY/06Z...THE DEEP SURFACE LOW IS
ABOUT 60 MILES NORTH NORTHEAST OF THE 06Z RUN SOUTH OF LONG
ISLAND. AT THE SAME TIME...THE 12Z GFS IS ABOUT 75 MILES WEST OF
THE 12Z NAM POSITION SOUTH OF SOUTHEAST MASSACHUSETTS.
THEREFORE...THE SPREAD BETWEEN THE TWO MODELS HAS DIMINISHED
SOMEWHAT INDICATING MORE OF A CONVERGENCE OF SOLUTIONS THOUGH THE
NAM REMAINS FARTHER EAST.

THE 12Z GEFS MEAN IS SIMILAR TO THE 12Z GFS OPERATIONAL RUN EXCEPT
IT IS SLIGHTLY FASTER WITH THE MOVEMENT OF THE SURFACE LOW UP THE
EAST COAST THAN THE 12Z RUN AND ACTUALLY TAKES THE SURFACE LOW
OVER CAPE COD BY 12Z MONDAY. THIS IS CLOSER TO THE COAST THAN ANY
OTHER 12Z OPERATIONAL RUN.

THE 12Z CANADIAN GLOBAL RUN IS QUITE CLOSE TO THE 12Z NAM IN
KEEPING THE CENTER OF LOW PRESSURE EAST OF THE 12Z GFS SOLUTION.
BY SUNDAY EVENING OR 00Z MONDAY/ THE CENTRAL PRESSURE AND LOCATION
OF THE SURFACE LOW IS NEARLY IDENTICAL TO THE 12Z NAM AND BY 12Z
MONDAY IS ABOUT 30 MILES EAST SOUTHEAST OF THE NAM POSITION EAST
OF NANTUCKET.

THE 12Z UKMET HAS ALSO CONVERGED TOWARD THE 00Z EUROPEAN/12Z GFS
AND IS SLIGHTLY FARTHER WEST AND SLOWER THAN THE 12Z NAM/CANADIAN
AND SLIGHTLY DEEPER. IT IS ACTUALLY THE SLOWEST AND FARTHEST SOUTH
OF THE RECENT RUNS AS THE LOW MOVES AWAY FROM SOUTHEAST NEW
ENGLAND AFTER 12Z MONDAY.

THE 12Z EUROPEAN IS VERY SIMILAR IN TRACK AND INTENSITY TO THE 00Z
RUN AND BY ITSELF COULD BE CONSIDERED A GOOD FORECAST CHOICE.
SINCE IT IS NOW RELATIVELY CLOSE TO ALL THE OTHER MODELS ANY
COMBINATION WOULD LIKELY GET A PRETTY REASONABLE FORECAST FOR THE
STORM. AS THE STORM PASSES OFF SOUTHEAST NEW ENGLAND...THE 12Z RUN
IS SLOWER THAN THE PREVIOUS VERSION AND SOMEWHAT RESEMBLES THE 12Z
UKMET...IMPLYING SLOWER ENDING TIMES FOR SNOW ACROSS EASTERN NEW
ENGLAND.

WITH THE CONVERGENCE OF ALL 12Z MODELS...MOST COMBINATION OF ANY
AND EACH WOULD PROBABLY MAKE FOR A GOOD BLEND.

SHORTWAVE APPROACHING SOUTHERN CALIFORNIA THAT MOVES ACROSS THE
SOUTHWEST...TO THE SOUTHERN PLAINS BY MONDAY MORNING AND MIDWEST
BY TUESDAY MORNING.

THE 12Z GFS IS FASTER THAN THE NAM WITH BRINGING THIS SYSTEM
EASTWARD INTO ARIZONA BY 18Z SUNDAY. BY TUESDAY/DAY 3...THE 12Z
NAM REMAINS SLOWER AND DEEPER THAN THE OTHER 12Z RUNS...WHILE THE
12Z GFS/EUROPEAN/UKMET/CANADIAN ARE FASTER AND SLIGHTLY WEAKER.  

PREFERENCE IS TO USE THE 12Z GFS/EUROPEAN/UKMET/GFS...AND NOT THE
12Z NAM

MAJOR TROUGH MOVING TOWARD THE PACIFIC NORTHWEST SUNDAY INTO
MONDAY...

THE 12Z NAM APPEARS TO ACCELERATE RELATIVE TO THE OTHER 12Z
OPERATIONAL MODELS BY MONDAY/DAY 2.  THE 12Z
GFS/UKMET/CANADIAN/ECMWF ARE FASTER THAN THE NAM AS THIS SYSTEM
MOVES EASTWARD ACROSS MONTANA BY 12Z MONDAY. BY 12Z TUESDAY...THE
NAM APPEARS TO BE THE NORTHERN/WESTERN OUTLIER COMPARED TO THE
OTHER 12Z RUNS WITH A PREFERENCE TOWARD USING THE 12Z GFS/12Z
EUROPEAN.

36
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Blizzard warning/watch to be issue at 4pm for tomorrow-mon.30-5omph winds,tides 3-6' above normal - Fred, 12/25/2010, 12:58 pm
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